Field of the Invention
The present invention relates to a discharge circuit, and especially relates to a circuit structure which is able to reduce circuit system loss.
Description of the Related Art
Semiconductor technologies are growing quickly, so that computers and peripherals are growing quickly as well. Power of integrated circuits (abbreviation as IC) applied to computers and peripherals are variously manufactured due to various power requirements. In order to satisfy various power requirements, the pulse width modulation regulators of the boost converter and the buck converter and so on are provided. This is one of the very important factors for providing various digital products.
In the abnormal condition, the output voltage of the pulse width modulator may exceed the rated limitation, so that the end-system which is powered by the power supply might be broken. Therefore, usually the over voltage protection (abbreviation as OVP) circuit is provided, so that the pulse width modulation regulator stops working to avoid the end-system from being broken when the output voltage exceeds the rated limitation.
A conventional over voltage protection circuit comprises a detection circuit arranged at the voltage output side of the pulse width modulator. The pulse width modulator stops working immediately when the detection circuit detects that the output voltage is too high.
A conventional output discharge circuit is to arrange a specific resistance at PSU output stage as a minimum load to speed up the discharge speed when OVP is triggered. Due to PSU's output voltage regulation needs, several hundred to thousands micro farad electrolytic capacitors are applied at the voltage output side of the power supply. When the load of voltage output side is at light or no load condition, the output voltage has to wait for a long period to go within the safe range after PSU stops working. However, the period is related to the capacitor capacitance. Somebody may be hurt if he/she touches the output voltage accidently before the output voltage goes within the safe range. Nevertheless, power conversion efficiency is reduced because resistive loss exists at the voltage output side of the power supply.
Therefore, in order to solve the above-mentioned problems, a solution is provided.